The class of polymers of carbon monoxide and olefin(s) has been known for a number of years. Brubaker, U.S. Pat. No. 2,495,286, produced such polymers of relatively low carbon monoxide content in the presence of free radical initiators, e.g., peroxy compounds. U.K. No. 1,081,304 produces similar polymers of higher carbon monoxide content in the presence of alkylphosphine complexes of palladium compounds as catalyst. Nozaki extended the process to produce linear alternating polymers in the presence of arylphosphine complexes of palladium moieties and certain inert solvents. See, for example, U.S. Pat. No. 3,694,412.
More recently, the class of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon has become of greater interest in part because of the greater availability of the polymers. The more recent general processes for the production of such polymers are illustrated by a number of published European Patent applications including Nos. 121,965, 181,014, 213,671, and 257,663. The process generally involves the use of a catalyst composition formed from a Group VIII metal selected from palladium, cobalt or nickel, the anion of a non-hydrohalogenic acid having a pKa below about 6, preferably below 2, and a bidentate ligand of phosphorous, arsenic or antimony. Although the scope of the polymerization process is extensive, a frequently preferred catalyst composition is formed from a palladium salt, particularly palladium acetate, the anion of trifluoroacetic acid or p-toluenesulfonic acid, and a bidentate ligand of phosphorus, particularly 1,3-bis(diphenylphosphino)-propane and 1,3-bis[di(2-methoxyphenyl)phosphino]propane. The resulting polymers, now considered conventional, are relatively high molecular weight materials having established utility as premium thermoplastics in the production of shaped articles produced by methods which are conventional for thermoplastics.
The process for the production of the linear alternating polymers typically comprises contacting the monomeric reactants, the catalyst composition and a reaction* diluent under polymerization conditions of elevated temperature and pressure and obtaining the polymer product in the form of a suspension in the reaction diluent. The polymer is then recovered by conventional methods such as filtration or decantation. Although the process for polymer production results in efficient production and recovery of polymer product in good yield, the process does result in some degree of reactor fouling as do most if not all polymerization processes. The polymer product that is deposited in the reactor, e.g., on reactor walls and baffle plates, represents an economic loss as well as necessitating the periodic removal of the deposited polymer by mechanical means. It would be of advantage to provide an improved process for the production of linear alternating polymers of carbon monoxide and at least one ethylenically unsaturated hydrocarbon, which process is characterized by a reduced level of reactor fouling.